1. Field of the Invention
The present invention relates to an organic EL display provided with an auxiliary wiring and a method of manufacturing the same.
2. Description of the Related Art
In recent years, attention is being paid to an organic EL element using an electro luminescence (EL) phenomenon of an organic material as a light emitting element capable of emitting high-luminance light by low-voltage DC driving. As a method of driving a display device (organic EL display) using the organic EL element, a simple matrix method and an active matrix method are mentioned. In the case where the number of pixels is large, the active matrix method is suitable.
In an organic EL display of the active matrix method, a thin film transistor for driving each pixel (organic EL element), a first electrode connected to the thin film transistor, an organic layer including a light emission layer, and a second electrode are provided in this order on a substrate. In such an organic EL display, to assure the aperture ratio of each pixel, it is preferable to extract light from the side opposite to the substrate, that is, to employ the surface emission structure (called “surface emission type” below). In the organic EL display of the surface emission type, the second electrode is made of a transparent or semi-transparent electrode material.
However, such a transparent electrode material has generally a high electric resistance value and the second electrode is formed as an electrode common to the pixels. Consequently, in an organic EL display of the surface emission type, a voltage drop easily occurs in the second electrode. It causes significant deterioration in display performance. To suppress occurrence of such a voltage drop, a method of providing an auxiliary wiring in a region between pixels is used. Concretely, an auxiliary wiring electrically insulated from the first electrode is disposed on the first electrode side on the substrate and is electrically connected to the second electrode.
In many cases, an organic layer is formed on an entire surface of the substrate. Since the organic layer is formed also on the auxiliary wiring, there is the possibility that contact between the auxiliary wiring and the second electrode deteriorates due to the organic layer. Even in the case of forming an organic layer on a pixel unit basis with a mask, if mask positioning precision or precision of processing the opening in the mask is low, the organic layer is formed on the auxiliary wiring, and it results in deterioration in contact with the second electrode.
Therefore, methods of selectively removing the organic layer on the auxiliary wiring by irradiating a region on the auxiliary wiring in the organic layer with a laser beam were proposed as described in, for example, Japanese Unexamined Patent Application Publication Nos. 2005-11810 and 2006-286493.